Gamma-ray Burst 151031A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 31 Oct 15 05:50:52 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     662330,   Seg_Num: 0
GRB_RA:           83.199d {+05h 32m 48s} (J2000),
                  83.331d {+05h 33m 19s} (current),
                  82.783d {+05h 31m 08s} (1950)
GRB_DEC:         -39.092d {-39d 05' 28"} (J2000),
                 -39.081d {-39d 04' 51"} (current),
                 -39.125d {-39d 07' 31"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       2246 [cnts]    Image_Peak=128 [image_cnts]
TRIGGER_DUR:     0.512 [sec] 
TRIGGER_INDEX:   121     E_range: 15-50 keV
BKG_INTEN:       27521 [cnts]
BKG_TIME:        21016.65 SOD {05:50:16.65} UT
BKG_DUR:         8 [sec]
GRB_DATE:        17326 TJD;   304 DOY;   15/10/31
GRB_TIME:        21030.34 SOD {05:50:30.34} UT
GRB_PHI:         -170.69 [deg]
GRB_THETA:        36.44 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     11.18 [sigma]
IMAGE_SIGNIF:    7.43 [sigma]
MERIT_PARAMS:     +1  +0  +0  -1  +1  -2  +0  +0 +34  +0 
SUN_POSTN:       215.13d {+14h 20m 31s}  -14.01d {-14d 00' 24"}
SUN_DIST:        110.45 [deg]   Sun_angle= 8.8 [hr] (West of Sun)
MOON_POSTN:       87.93d {+05h 51m 42s}  +18.27d {+18d 16' 02"}
MOON_DIST:        57.51 [deg]
MOON_ILLUM:      82 [%]
GAL_COORDS:      244.10,-31.33 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       78.61,-62.26 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Coordinates.  
COMMENTS:        This is a rate trigger.  
COMMENTS:        A point_source was found.  
COMMENTS:        This does not match any source in the on-board catalog.  
COMMENTS:        This does not match any source in the ground catalog.  
COMMENTS:        This is a GRB.  
COMMENTS:        This trigger occurred at longitude,latitude = 223.21,7.10 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 31 Oct 15 05:54:29 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     662330,   Seg_Num: 0
GRB_RA:           83.199d {+05h 32m 48s} (J2000),
                  83.331d {+05h 33m 19s} (current),
                  82.783d {+05h 31m 08s} (1950)
GRB_DEC:         -39.092d {-39d 05' 28"} (J2000),
                 -39.081d {-39d 04' 51"} (current),
                 -39.125d {-39d 07' 31"} (1950)
GRB_DATE:        17326 TJD;   304 DOY;   15/10/31
GRB_TIME:        21030.34 SOD {05:50:30.34} UT
TRIGGER_INDEX:   121
GRB_PHI:         -170.69 [deg]
GRB_THETA:        36.44 [deg]
DELTA_TIME:      71.00 [sec]
TRIGGER_DUR:     0.512 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     11.18 [sigma]
IMAGE_SIGNIF:    7.43 [sigma]
LC_URL:          sw00662330000msb.lc
SUN_POSTN:       215.13d {+14h 20m 32s}  -14.01d {-14d 00' 27"}
SUN_DIST:        110.45 [deg]   Sun_angle= 8.8 [hr] (West of Sun)
MOON_POSTN:       87.96d {+05h 51m 51s}  +18.27d {+18d 16' 03"}
MOON_DIST:        57.51 [deg]
MOON_ILLUM:      82 [%]
GAL_COORDS:      244.10,-31.33 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       78.61,-62.26 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Lightcurve.  
COMMENTS:           
COMMENTS:        The next comments were copied from the BAT_POS Notice:  
COMMENTS:        This is a rate trigger.  
COMMENTS:        A point_source was found.  
COMMENTS:        This does not match any source in the on-board catalog.  
COMMENTS:        This does not match any source in the ground catalog.  
COMMENTS:        This is a GRB.  
COMMENTS:        This trigger occurred at longitude,latitude = 223.21,7.10 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 31 Oct 15 05:58:03 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     662330,   Seg_Num: 0
POINT_RA:         83.176d {+05h 32m 42s} (J2000)
POINT_DEC:       -39.086d {-39d 05' 08"} (J2000)
IMG_START_DATE:  17326 TJD;   304 DOY;   15/10/31
IMG_START_TIME:  21463.96 SOD {05:57:43.96} UT,   433.6 [sec] since BAT Trigger Time
COUNTS:          1    Min_needed= 20
STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER:        0    Max_iter_allowed= 4
ERROR_CODE:      1
COMMENTS:        SWIFT-XRT Nack Position.  
COMMENTS:        No source found in the image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 31 Oct 15 06:00:44 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     662330,   Seg_Num: 0
POINT_RA:         83.177d {+05h 32m 42s} (J2000)
POINT_DEC:       -39.086d {-39d 05' 08"} (J2000)
POINT_ROLL:      129.616d
IMG_START_DATE:  17326 TJD;   304 DOY;   15/10/31
IMG_START_TIME:  21469.48 SOD {05:57:49.48} UT,   439.1 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.537
N_STARS:         112
X_OFFSET:        582 [pixels]
Y_OFFSET:        453 [pixels]
X_MAX:           1541 [pixels]
Y_MAX:           1412 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw00662330000msufc0439.fits
SUN_POSTN:       215.14d {+14h 20m 33s}  -14.01d {-14d 00' 32"}
SUN_DIST:        110.47 [deg]   Sun_angle= 8.8 [hr] (West of Sun)
MOON_POSTN:       88.03d {+05h 52m 06s}  +18.27d {+18d 16' 05"}
MOON_DIST:        57.51 [deg]
MOON_ILLUM:      82 [%]
GAL_COORDS:      244.09,-31.34 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       78.57,-62.25 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 31 Oct 15 06:01:28 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     662330,   Seg_Num: 0
POINT_RA:         83.177d {+05h 32m 42s} (J2000)
POINT_DEC:       -39.086d {-39d 05' 08"} (J2000)
POINT_ROLL:      129.616d
IMG_START_DATE:  17326 TJD;   304 DOY;   15/10/31
IMG_START_TIME:  21469.48 SOD {05:57:49.48} UT,   439.1 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.537
N_STARS:         112
X_OFFSET:        582 [pixels]
Y_OFFSET:        453 [pixels]
X_MAX:           1541 [pixels]
Y_MAX:           1412 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw00662330000msufc0439.fits
SUN_POSTN:       215.14d {+14h 20m 33s}  -14.01d {-14d 00' 32"}
SUN_DIST:        110.47 [deg]   Sun_angle= 8.8 [hr] (West of Sun)
MOON_POSTN:       88.03d {+05h 52m 08s}  +18.27d {+18d 16' 05"}
MOON_DIST:        57.51 [deg]
MOON_ILLUM:      82 [%]
GAL_COORDS:      244.09,-31.34 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       78.57,-62.25 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 31 Oct 15 06:02:14 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     662330,   Seg_Num: 0
GRB_RA:           83.1953d {+05h 32m 46.87s} (J2000),
                  83.3270d {+05h 33m 18.47s} (current),
                  82.7796d {+05h 31m 07.11s} (1950)
GRB_DEC:         -39.1204d {-39d 07' 13.4"} (J2000),
                 -39.1101d {-39d 06' 36.2"} (current),
                 -39.1544d {-39d 09' 15.8"} (1950)
GRB_ERROR:       4.1 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  17326 TJD;   304 DOY;   15/10/31
IMG_START_TIME:  21481.00 SOD {05:58:01.00} UT,   450.7 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       215.14d {+14h 20m 33s}  -14.01d {-14d 00' 33"}
SUN_DIST:        110.44 [deg]   Sun_angle= 8.8 [hr] (West of Sun)
MOON_POSTN:       88.04d {+05h 52m 10s}  +18.27d {+18d 16' 06"}
MOON_DIST:        57.55 [deg]
MOON_ILLUM:      82 [%]
GAL_COORDS:      244.13,-31.34 [deg] galactic lon,lat of the burst
ECL_COORDS:       78.60,-62.29 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        TAM values, flux and significance fields are not valid.  
COMMENTS:        This position was automatically generated on the ground using  
COMMENTS:        Photon Counting data telemetered via TDRSS (SPER data).  
COMMENTS:        See http://www.swift.ac.uk/sper/docs.php for details.  
COMMENTS:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 0.58% < P(seren) < 1.1%.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 31 Oct 15 06:03:19 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     662330,   Seg_Num: 0
POINT_RA:         83.177d {+05h 32m 42s} (J2000)
POINT_DEC:       -39.086d {-39d 05' 08"} (J2000)
ROLL:            129.616d
IMG_START_DATE:  17326 TJD;   304 DOY;   15/10/31
IMG_START_TIME:  21469.48 SOD {05:57:49.48} UT,   439.1 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     467963884
X_OFFSET:        901 [pixels]
Y_OFFSET:        772 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1061
Y_GRB_POS:       932
BINNING_INDEX:   1
IM_URL:          sw00662330000msuni0455.fits
SUN_POSTN:       215.14d {+14h 20m 33s}  -14.01d {-14d 00' 34"}
SUN_DIST:        110.47 [deg]   Sun_angle= 8.8 [hr] (West of Sun)
MOON_POSTN:       88.05d {+05h 52m 12s}  +18.27d {+18d 16' 06"}
MOON_DIST:        57.52 [deg]
MOON_ILLUM:      82 [%]
GAL_COORDS:      244.09,-31.34 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       78.57,-62.25 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        This notice was forced out after watchdog timer expiring -- most likely due to missing packet(s);  
COMMENTS:        as a consequence some of the fields may be incoorect (eg TRIGGER_NUM,RA,DEC).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 31 Oct 15 06:03:27 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     662330,   Seg_Num: 0
POINT_RA:         83.177d {+05h 32m 42s} (J2000)
POINT_DEC:       -39.086d {-39d 05' 08"} (J2000)
ROLL:            129.616d
IMG_START_DATE:  17326 TJD;   304 DOY;   15/10/31
IMG_START_TIME:  21469.48 SOD {05:57:49.48} UT,   439.1 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     467963884
X_OFFSET:        901 [pixels]
Y_OFFSET:        772 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1061
Y_GRB_POS:       932
BINNING_INDEX:   1
IM_URL:          sw00662330000msuni0455.fits
SUN_POSTN:       215.14d {+14h 20m 33s}  -14.01d {-14d 00' 34"}
SUN_DIST:        110.47 [deg]   Sun_angle= 8.8 [hr] (West of Sun)
MOON_POSTN:       88.05d {+05h 52m 13s}  +18.27d {+18d 16' 06"}
MOON_DIST:        57.52 [deg]
MOON_ILLUM:      82 [%]
GAL_COORDS:      244.09,-31.34 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       78.57,-62.25 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        All 4 attachments are included.  
COMMENTS:        This notice was forced out after watchdog timer expiring -- most likely due to missing packet(s);  
COMMENTS:        as a consequence some of the fields may be incoorect (eg TRIGGER_NUM,RA,DEC).

GCN Circular #18538
E. Sonbas (Adiyaman Univ.), V. D'Elia (ASDC), L. Izzo (URoma/ICRA), J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA) and D. M. Palmer (LANL) report on behalf of the Swift Team:
At 05:50:30 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 151031A (trigger=662330). Swift slewed to the burst after a 6 minute delay due to viewing constraints. The BAT on-board calculated location is RA, Dec 83.199, -39.092 which is
```
   RA(J2000) = 05h 32m 48s
   Dec(J2000) = -39d 05' 28"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single-peaked structure with a duration of about 10 sec. The peak count rate was ~2500 counts/sec (15-350 keV), at ~2 sec after the trigger.
The XRT began observing the field at 05:57:43.9 UT, 433.6 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 83.19532, -39.12049 which is equivalent to:
```
   RA(J2000)  = 05h 32m 46.88s
   Dec(J2000) = -39d 07' 13.8"
```
with an uncertainty of 4.1 arcseconds (radius, 90% containment). This location is 103 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. We cannot determine whether the source is fading at the present time.
A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 2.62 x 10^20 cm^-2 (Willingale et al. 2013).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 439 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers none of the XRT error circle. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.03.
Burst Advocate for this burst is E. Sonbas (edasonbas AT yahoo.com). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/too.html.)

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 31 Oct 15 06:20:32 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     662330,   Seg_Num: 0
POINT_RA:         83.175d {+05h 32m 42s} (J2000)
POINT_DEC:       -39.083d {-39d 04' 57"} (J2000)
POINT_ROLL:      129.616d
IMG_START_DATE:  17326 TJD;   304 DOY;   15/10/31
IMG_START_TIME:  21900.78 SOD {06:05:00.78} UT,   870.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.468
N_STARS:         190
X_OFFSET:        342 [pixels]
Y_OFFSET:        213 [pixels]
X_MAX:           1781 [pixels]
Y_MAX:           1652 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw00662330000msufc0870.fits
SUN_POSTN:       215.15d {+14h 20m 36s}  -14.01d {-14d 00' 48"}
SUN_DIST:        110.48 [deg]   Sun_angle= 8.8 [hr] (West of Sun)
MOON_POSTN:       88.23d {+05h 52m 54s}  +18.27d {+18d 16' 10"}
MOON_DIST:        57.53 [deg]
MOON_ILLUM:      82 [%]
GAL_COORDS:      244.09,-31.34 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       78.57,-62.25 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 31 Oct 15 06:20:55 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     662330,   Seg_Num: 0
POINT_RA:         83.175d {+05h 32m 42s} (J2000)
POINT_DEC:       -39.083d {-39d 04' 57"} (J2000)
POINT_ROLL:      129.616d
IMG_START_DATE:  17326 TJD;   304 DOY;   15/10/31
IMG_START_TIME:  21900.78 SOD {06:05:00.78} UT,   870.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.468
N_STARS:         190
X_OFFSET:        342 [pixels]
Y_OFFSET:        213 [pixels]
X_MAX:           1781 [pixels]
Y_MAX:           1652 [pixels]
DET_THRESH:      10
PHOTO_THRESH:    5
SL_URL:          sw00662330000msufc0870.fits
SUN_POSTN:       215.15d {+14h 20m 36s}  -14.01d {-14d 00' 48"}
SUN_DIST:        110.48 [deg]   Sun_angle= 8.8 [hr] (West of Sun)
MOON_POSTN:       88.23d {+05h 52m 55s}  +18.27d {+18d 16' 10"}
MOON_DIST:        57.53 [deg]
MOON_ILLUM:      82 [%]
GAL_COORDS:      244.09,-31.34 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       78.57,-62.25 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 31 Oct 15 06:21:17 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     662330,   Seg_Num: 0
GRB_RA:           83.1966d {+05h 32m 47.18s} (J2000),
                  83.3283d {+05h 33m 18.78s} (current),
                  82.7809d {+05h 31m 07.42s} (1950)
GRB_DEC:         -39.1214d {-39d 07' 17.0"} (J2000),
                 -39.1111d {-39d 06' 39.8"} (current),
                 -39.1554d {-39d 09' 19.3"} (1950)
GRB_ERROR:       2.4 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  17326 TJD;   304 DOY;   15/10/31
IMG_START_TIME:  21481.00 SOD {05:58:01.00} UT,   450.7 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       215.15d {+14h 20m 36s}  -14.01d {-14d 00' 48"}
SUN_DIST:        110.44 [deg]   Sun_angle= 8.8 [hr] (West of Sun)
MOON_POSTN:       88.23d {+05h 52m 56s}  +18.27d {+18d 16' 11"}
MOON_DIST:        57.56 [deg]
MOON_ILLUM:      82 [%]
GAL_COORDS:      244.14,-31.33 [deg] galactic lon,lat of the burst
ECL_COORDS:       78.60,-62.29 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        This is an Update Notice -- the RA,Dec values herein supersede the previous XRT_POS Notice.  
COMMENTS:        TAM values, flux and significance fields are not valid.  
COMMENTS:        This position was automatically generated on the ground using  
COMMENTS:        Photon Counting data telemetered via TDRSS (SPER data).  
COMMENTS:        See http://www.swift.ac.uk/sper/docs.php for details.  
COMMENTS:        This position was enhanced using UVOT field astrometry.  
COMMENTS:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 0.58% < P(seren) < 1.1%.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 31 Oct 15 06:22:00 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     662330,   Seg_Num: 0
POINT_RA:         83.175d {+05h 32m 42s} (J2000)
POINT_DEC:       -39.083d {-39d 04' 57"} (J2000)
ROLL:            129.616d
IMG_START_DATE:  17326 TJD;   304 DOY;   15/10/31
IMG_START_TIME:  21900.78 SOD {06:05:00.78} UT,   870.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     467964316
X_OFFSET:        901 [pixels]
Y_OFFSET:        772 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1061
Y_GRB_POS:       932
BINNING_INDEX:   1
IM_URL:          sw00662330000msuni0886.fits
SUN_POSTN:       215.15d {+14h 20m 36s}  -14.01d {-14d 00' 49"}
SUN_DIST:        110.48 [deg]   Sun_angle= 8.8 [hr] (West of Sun)
MOON_POSTN:       88.24d {+05h 52m 58s}  +18.27d {+18d 16' 11"}
MOON_DIST:        57.53 [deg]
MOON_ILLUM:      82 [%]
GAL_COORDS:      244.09,-31.34 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       78.57,-62.25 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 31 Oct 15 06:22:13 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     662330,   Seg_Num: 0
POINT_RA:         83.175d {+05h 32m 42s} (J2000)
POINT_DEC:       -39.083d {-39d 04' 57"} (J2000)
ROLL:            129.616d
IMG_START_DATE:  17326 TJD;   304 DOY;   15/10/31
IMG_START_TIME:  21900.78 SOD {06:05:00.78} UT,   870.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     467964316
X_OFFSET:        901 [pixels]
Y_OFFSET:        772 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1061
Y_GRB_POS:       932
BINNING_INDEX:   1
IM_URL:          sw00662330000msuni0886.fits
SUN_POSTN:       215.15d {+14h 20m 36s}  -14.01d {-14d 00' 49"}
SUN_DIST:        110.48 [deg]   Sun_angle= 8.8 [hr] (West of Sun)
MOON_POSTN:       88.24d {+05h 52m 58s}  +18.27d {+18d 16' 11"}
MOON_DIST:        57.53 [deg]
MOON_ILLUM:      82 [%]
GAL_COORDS:      244.09,-31.34 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       78.57,-62.25 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        All 4 attachments are included.

GCN Circular #18540
D. Malesani (DARK/NBI), N. R. Tanvir (Univ. Leicester), T. Kruehler (MPE), A. de Ugarte Postigo (IAA-CSIC and DARK/NBI), H. Flores (GEPI/Paris obs), D. Xu (NAOC/CAS), J.P.U. Fynbo (DARK/NBI), report on behalf of the X-shooter GRB collaboration:
We observed the field of GRB 151031A (Sonbas et al., GCN 18538) with the ESO Very Large Telescope UT2 (Kueyen) equipped with the X-shooter spectrograph. Observations were carried out using the automatic "rapid response mode" (RRM), and started immediately following the reception of the XRT position notice.
In the acquisition images, we detect a single source consistent with the position of the XRT afterglow, at coordinates (J2000):
```
RA = 05:32:47.11
Dec = -39:07:19.1
```
We measure for this object R = 20.4 +- 0.1 (calibrated against three nearby USNO stars) in an image taken on Oct 31.2565 UT, that is 18.8 min after the GRB.
A sequence of spectra with increasing exposure time (3 to 32 min) was secured covering the wavelength range 3,000 - 25,000 AA. From the analysis of the first 8 min data, several absorption features can be seen on top of the object continuum, which we interpret as due to Ca II, Mg I, Mg II and Fe II in absorption at a common redshift of z = 1.167. In the visible arm, an emission feature is also seen, corresponding to [O ii] at a consistent redshift, which we thus consider to be the redshift of GRB 151031A. Analysis of the full data set is ongoing.
We acknowledge excellent support from the ESO observing staff in Paranal, in particular Thomas Rivinius, Marcela Espinoza, and Claudia Cid.
GCN Circular #18541
P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team.
Using 436 s of XRT Photon Counting mode data and 1 UVOT images for GRB 151031A, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 83.19596, -39.12134 which is equivalent to:
```
RA (J2000): 05h 32m 47.03s
Dec (J2000): -39d 07' 16.8"
```
with an uncertainty of 2.2 arcsec (radius, 90% confidence).
This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177).
This circular was automatically generated, and is an official product of the Swift-XRT team.
GCN Circular #18542
T. N. Ukwatta (LANL),S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA),A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), E. Sonbas (Adiyaman Univ.), M. Stamatikos (OSU), (i.e. the Swift-BAT team):
Using the data set from T-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 151031A (trigger #662330) (Sonbas, et al., GCN Circ. 18538). The BAT ground-calculated position is RA, Dec = 83.189, -39.125 deg which is
```
    RA(J2000)  =  05h 32m 45.3s
    Dec(J2000) = -39d 07' 28.3"
```
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment). The partial coding was 67%.
The mask-weighted light curve shows a single FRED-shaped peak, peaking at T+2 sec and returning to background by T+7 sec. T90 (15-350 keV) is 5.00 +- 2.24 sec (estimated error including systematics).
The time-averaged spectrum from T+0.30 to T+6.30 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.41 +- 0.18. The fluence in the 15-150 keV band is 3.2 +- 0.3 x 10^-7erg/cm2. The 1-sec peak photon flux measured from T+1.30 sec in the 15-150 keV band is 1.7 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level.
The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/662330/BA/
GCN Circular #18544
A. Maselli (INAF-IASFPA), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), T.G.R. Roegiers (PSU), P.A. Evans (U. Leicester), S.L. Gibson (U. Leicester), J.P. Osborne (U. Leicester), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB) and E. Sonbas report on behalf of the Swift-XRT team:
We have analysed 7.5 ks of XRT data for GRB 151031A (Sonbas et al. GCN Circ. 18538), from 443 s to 25.5 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Evans et al. (GCN Circ. 18541).
The light curve can be modelled with a power-law decay with a decay index of alpha=0.56 (+/-0.07).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.13 (+0.22, -0.21). The best-fitting absorption column is 9.4 (+3.8, -3.3) x 10^21 cm^-2, at a redshift of 1.167, in addition to the Galactic value of 2.6 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.2 x 10^-11 (4.6 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Galactic foreground: 2.6 x 10^20 cm^-2
Intrinsic column:    9.4 (+3.8, -3.3) x 10^21 cm^-2 at z=1.167
Photon index:	     2.13 (+0.22, -0.21)
```
If the light curve continues to decay with a power-law decay index of 0.56, the count rate at T+24 hours will be 0.010 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.3 x 10^-13 (4.7 x 10^-13) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00662330.
This circular is an official product of the Swift-XRT team.
GCN Circular #18546
N. P. M. Kuin (UCL-MSSL) and E. Sonbas (Adiyaman Univ.) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 151031A 439 s after the BAT trigger (Sonbas et al., GCN Circ. 18538). A source at the VLT position (Malesani et al, GCN Circ. 18540) and consistent with the XRT position (Evans et al. GCN Circ. 18541) is detected in the initial UVOT exposures.
Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)           Mag

white              439         1020          314         20.63 +/- 0.16
v                  595         8257          627        >20.1
b                  695         7642          588        >20.2
u                  670         7437          430         20.34 +/- 0.28
w1                 645         8677          635        >20.0
m2                 620         8462          627        >20.0
w2                 746         8053          607        >21.0
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.03 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #18547
D. Kuroda, K. Yanagisawa, Y. Shimizu, H. Toda (OAO, NAOJ), S. Nagayama (NAOJ), M. Yoshida (Hiroshima), K. Ohta (Kyoto) and N. Kawai(Tokyo Tech) report on behalf of MITSuME and OISTER collaboration:
We observed the field of GRB 151031A (Sonbas et al., GCNC 18538) with the optical three color (g', Rc and Ic) CCD camera attached to the MITSuME 50cm telescope of Okayama Astrophysical Observatory.
The observation started on 2015-10-31 15:54:27 UT (10.1 h after the burst). We could not detect the previously reported afterglow (Malesani et al., GCNC 18540; Kuin and Sonbas, GCNC 18546) in all the three bands.
Three sigma upper limits of the OT are listed below. We used GSC2.3 catalog for flux calibration.
```
#T0+[day]  MID-UT    T-EXP[sec]   g'    Rc     Ic
-----------------------------------------------------
0.49617    17:44:59    6000.0   >18.6  >18.9  >18.5
-----------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]
```
GCN Circular #18550
S. Schmidl (TLS Tautenburg), J. Graham, and J. Greiner (both MPE Garching) report on behalf of the GROND team:
We observed the field of GRB 151031A (SWIFT trigger 662330; Sonbas et al, GCN 18538) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2m MPG telescope at ESO La Silla Observatory (Chile).
Observations started on November 1, 2015, at 06:42 UT, 1.04 days after the GRB trigger (due to being clouded out the previous night). They were performed at an average seeing of 1.52" and at an average airmass of 1.02.
We detect the source reported by Malesani et al. (GCN 18540) and Kuin et al. (GCN 18546).
Based on total exposures of 33 minutes in g'r'i'z' and 72 minutes in JHK, we measure the following preliminary magnitudes and upper limits (AB magnitude system):
```
g' = 22.1 +/- 0.1 mag,
r' = 21.9 +/- 0.1 mag,
i' = 21.7 +/- 0.1 mag,
z' = 21.5 +/- 0.1 mag,
J  = 21.6 +/- 0.3 mag,
H  = 20.7 +/- 0.3 mag, and
K  > 19.8 mag.
```
Given magnitudes and upper limits are calibrated against GROND Zeropoints as well as 2MASS field stars and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V) = 0.03 mag in the direction of the burst (Schlegel et al. 1998).
GCN Circular #18551
T.Fujiwara, T. Yoshii, Y. Saito, Y. Tachibana, Y. Yano, Y.Ono, S.Harita, Y.Muraki, Y. Yatsu, and N. Kawai (Tokyo Tech)
report on behalf of the MITSuME collaboration:
We searched for the optical counterpart of GRB 151031A (E. Sonbas et al., GCN Circular #18538) with the optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm telescope of Akeno Observatory, Yamanashi, Japan.
The observation started on 2015-10-31 16:18:19 UT (10.5 h after the burst). We did not find any new point source within XRT circle in all three bands.
We obtained following limits for the magnitudes.
```
T0+[sec] MID-UT T-EXP[sec] g' Rc Ic
----------------------------------------------------------
37669  17:00:37  4440  > 18.8  > 18.9  > 18.3
----------------------------------------------------------
T0+ : Elapsed time after the burst 
T-EXP: Total Exposure time 
```
We used GSC2.3 catalog for flux calibration.

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Jochen Greiner, last update: 02-Nov-2015 [Disclaimer]